The present invention relates to conduit connectors and more particularly to connectors employed with flowlines and the like employed in undersea drilling and pumping operations.
Undersea drilling operations afford a unique environment requiring specially adapted equipment. In normal surface drilling operations, the wellhead from whence the drilling operation proceeds into the earth's surface is easily accessible to the operating personnel. By contrast, in undersea drilling operations the operating personnel are located in a floating platform or vessel on the ocean's surface with the wellhead disposed on the ocean floor many feet below. To communicate with the wellhead, guidelines are provided between the wellhead and the floating platform. The various conduits for flow between the surface and the wellhead are guided into position along the aforementioned guidelines. The connectors employed in such flow conduits, must, therefore, be connectable and disconnectable from the floating platform on the ocean's surface.
The main riser is the primary conduit of the system. Accordingly, its placement is of primary concern. The main conduit connector passes through the "Christmas tree" which forms the principal valving structure of the assembly. Disposed about the main riser connector are a plurality of smaller connectors for the smaller conduits or flowlines of the system. These auxiliary flowlines must be adapted for connection on a secondary basis. That is, the main riser conduit connector is typically seated and connected first followed by alignment and connection of the auxiliary connectors.
To allow for such secondary connection, it has been typical in such apparatus to provide the flowline connectors with a fairly loose fit to provide alignment and to then seal the connection therebetween when the two portions of the connector are slipped into concentric engagement by a deformable seal activated by fluid pressure provided by an auxiliary line from the surface. For example, an annular rubber bladder can be disposed to be positioned between the outer portion of the connector and the inner portion of the connector. When filled with fluid, such a bladder expands to fill the space therebetween to provide a leak-proof seal. While being leak-proof, such a deformable material employed as the primary seal has numerous drawbacks. First of all, the connection is not rigid. Thus, as the flowline is moved about by the ocean currents the flexing forces imposed therein are transmitted to the connector as the weakest point in the line. Moreover, such deformable material is prone to leak producing gouging and the like as a function of the mating process with the metallic components of the connector. The damage problem to the internal components of the connector is also augmented by the nature of the connector itself. Being typically a pair of concentrically interlocking conduit elements, engagement must be begun while the main riser connector is being maneuvered into position. That is, when the main riser connector has been completely seated and locked, the auxiliary connectors for the flowlines must have been concentrically engaged in the process and be ready for sealing.
Another drawback of prior art flowline connectors employed in subsea drilling operations is the total reliance on a surface controlled signal for the activation of the subsea in-line valves provided in the flowlines. That is, each of the flowlines is typically provided with an in-line valve at the wellhead. As the flowline is connected, a control line carried in combination therewith is simultaneously connected. Upon activation of a control signal through the control line, the in-line valve is opened to allow flow of fluid from the wellhead through the flowline. Once the surface signal opens the valve, the fluid will flow into the flowline regardless of the successful connection of the flowline connector. It would be desirable to have the flowline connection and the control signal to the in-line flow valve in interactive combination whereby in the event of an incomplete flowline connection, the control signal from the surface would be unable to open the in-line valve.
Wherefore, it is the objective of the present invention to provide a flowline connector for subsea operations which is provided with a metal-to-metal connection providing rigidity of the connector wherein the connector can be left in total disengagement until the main flowline connector has been positioned and locked guaranteeing positional alignment of the flowline connector and wherein the control line providing the signal to the in-line valve associated with the flowline being connected has continuity established therethrough only in the event of complete connection and locking of the flowline connector.